1. Field
Aspects of the present disclosure generally relate to the fabrication of devices, and more specifically to methods of depositing films used in devices.
2. Description of the Related Art
Silicon oxide (SiOx) films are commercially significant in numerous applications, such as in thin film transistors (TFTs) and active matrix organic light emitting diode (AMOLED) displays. SiOx films, such as SiOx films formed from tetraethyl orthosilicate (TEOS), perform better in those applications when the thicknesses of the deposited SiOx films are precisely controlled.
Conventional deposition processes are performed within “cleaning cycles.” Before a film is deposited on a substrate, the processing chamber is cleaned. After cleaning is complete, a series of substrates enter the processing chamber and films are deposited thereon. For example, the substrates may enter the processing chamber one at a time. As the series of substrates undergo deposition processes, unwanted material builds up on processing chamber surfaces. The unwanted material may affect further processing, such as by causing particle contamination. Particle contamination may cause device failure. After a certain number of substrates are processed, the chamber is cleaned again in order to remove the unwanted material. The time period between cleanings, often measured in the number of substrates processed, is referred to as the cleaning cycle. For example, a cleaning cycle may include the processing of six to eight substrates.
In conventional SiOx processing, the rate of SiOx deposition increases (i.e., the rate drifts) within each cleaning cycle. The rate drift undermines the device performance that can be obtained from precisely controlling the thicknesses of the SiOx films. Efforts have been taken to reduce the rate drift (i.e., to stabilize the deposition rate). However such efforts have been unsatisfactory to device manufacturers.
Therefore, what is need in the art is an improved technique for reducing rate drift in film deposition process, such as SiOx deposition processes.